Warranty polish: hero badges everywhere, search/pagination, re-check, shared apiError

- Shared utils/apiError.js reads the correct nested error message (with
  fallbacks); swept 37 views/components off the shallow path so real backend
  messages (e.g. in-use 409s) surface instead of generic "Failed".
- useWarrantyBadge composable: warranty hero status/end-date badge now on PC,
  equipment, printer, and network detail heroes (one shared fetch feeds the
  badge + the WarrantyPanel).
- Warranties list: client-side search (vendor/level/tag/asset) + pagination;
  truncate long service levels so they stop blowing out the table width.
- "Re-check all" button + POST /warranty/sync/dell?all=true to re-pull dated
  Dell warranties, not just missing ones.
- Deprecate the standalone pxe-images/warranty_sync.py in favor of the plugin.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/views/settings/BusinessUnitsList.vue

@@ -102,6 +102,7 @@ import { ref, onMounted } from 'vue'
 import { businessunitsApi } from '../../api'
 import PaginationBar from '../../components/PaginationBar.vue'
 import { useToast } from '../../composables/toast'
+import { apiError } from '../../utils/apiError'
 const toast = useToast()
 
 const items = ref([])
@@ -168,7 +169,7 @@ async function save() {
     closeModal()
     loadData()
   } catch (err) {
-    error.value = err.response?.data?.message || 'Failed to save'
+    error.value = apiError(err, 'Failed to save')
   } finally {
     saving.value = false
   }